The carb again - pops and splutters

[Machismo]

Happy new year to all bull riders out there!

Despite different combinations of pilot jet/main jet/needle positions(UCAL BS29 carb), my bike seems to pop horrendously. Right now the main jet s 120, pilot is 15 and needle raised one notch.
Air screw is about 4 turns out - the bike doesnt pull well at all.
Its a goldstar exhaust and a DU100 K&N air filter in the stock air box.
No air leaks in the intake or exhaust routes.

I had tried a 17.5 pilot before this but then the plug goes sooty.

Another question is: During tuning the air screw, I try to open up the air screw to get to the point where the RPM reaches the peak and then drops, this point never seem to show up at all!
Any ideas why this is so?
Perplexed, annoyed and fingers crossed 

Thanks guys!
Sudhir

[barenekd]

Not real familiar with that carb, but screwing the air screw in should make it richer. I'd try two or three turns out from the stop and see wht that does. You're too lean as it is.
Bare

[dampking]

Even I faced similar issues with BS29 when I had it in my bike. 17.5 pilot was good but it was a bit too rich. I did put the needle back in 2nd notch with the 17,5 pilot and it worked pretty well.. better than 17.5 in lowest notch.

[boggy]

Agreed about your air screw.  Better to run a little richer than leaner - Screw that baby all the way in and back it out 2 full turns.

Your carb may have a lot more thread than mine, but I don't believe there is even enough room to wind it out 4 turns on a PWK.

[DanB]

The air screw is actually a volume control screw on the CV carb. Clockwise leans it; counterclockwise enriches. I'm still on a 15 pilot with partial free flow exhaust. It takes just a little bit turning the VC screw to get the idle to change. Not much at all. Starting from 2 to 3 full turns out is a good start point. Make sure the bike is warmed up.

Search on in the general gallery for a few data sheets on the BS29 I found. I like the one below

[Machismo]

The air screw is actually a volume control screw on the CV carb. Clockwise leans it; counterclockwise enriches. I'm still on a 15 pilot with partial free flow exhaust. It takes just a little bit turning the VC screw to get the idle to change. Not much at all. Starting from 2 to 3 full turns out is a good start point. Make sure the bike is warmed up.

Search on in the general gallery for a few data sheets on the BS29 I found. I like the one below

Very informative images Dan. I am gonna hit my usual freeway here in the weekend and try tuning with a 17.5 pilot and 15, if the former doesnt work.
Are you on the stock air filter?

Agreed about your air screw.  Better to run a little richer than leaner - Screw that baby all the way in and back it out 2 full turns.

Your carb may have a lot more thread than mine, but I don't believe there is even enough room to wind it out 4 turns on a PWK.

Yeah, the BS29 has lot of thread, i could remember it as more than 9 turns when i opened it up for cleaning. Its already 4 turns out Boggy, and still pops.

Even I faced similar issues with BS29 when I had it in my bike. 17.5 pilot was good but it was a bit too rich. I did put the needle back in 2nd notch with the 17,5 pilot and it worked pretty well.. better than 17.5 in lowest notch.

Exactly, 15 seems too lean and 17.5 appears to be too rich.
Quite an issue 

Not real familiar with that carb, but screwing the air screw in should make it richer. I'd try two or three turns out from the stop and see wht that does. You're too lean as it is.
Bare

This carb's air screw does the reverse Bare - clockwise leans it out.
I am gonna post an update after another attempt at getting the magical jet/air screw turns!

Does the ambient temperature effect the tuning? Because I have always noticed that sometimes the bike runs well in the day and bit blunt in the night or vice-verse.

[motomataya]

Not always but usually if the screw is on the engine side it's a fuel screw. Air box side, its a air bleed screw.

[tooseevee]

Happy new year to all bull riders out there!

Despite different combinations of pilot jet/main jet/needle positions(UCAL BS29 carb), my bike seems to pop horrendously. Right now the main jet s 120, pilot is 15 and needle raised one notch.
Air screw is about 4 turns out - the bike doesnt pull well at all.
Its a goldstar exhaust and a DU100 K&N air filter in the stock air box.
No air leaks in the intake or exhaust routes.

I had tried a 17.5 pilot before this but then the plug goes sooty.

Another question is: During tuning the air screw, I try to open up the air screw to get to the point where the RPM reaches the peak and then drops, this point never seem to show up at all!
Any ideas why this is so?
Perplexed, annoyed and fingers crossed 

Thanks guys!
Sudhir

        I've done a lot of playing around with this carb on my '08 Classic (bought with zero miles from an out of business dealer). I put 300 miles on it & went to an open exhaust & a K&N.

         First off, that's not an air screw. It regulates fuel; Clockwise to lean.

         After much back & forth (I probably had the carb off & on a dozen times dialing it in) I'm back to the stock 15 Pilot & the stock 110 Main with the needle lifted two shims. My needle has the permanent plastic collar on it over the notches so I can't talk notches with you. My mixture screw is about 1 1/2 turns out.

         The bike runs perfectly set up this way & now has 600 miles. It kick starts under all conditions with one or two kicks (I never use the ES) & never dies at stop signs or pops or sputters or any other bad stuff. It pulls well in the first 4 gears up to my break-in speeds. I've only even been in 5th a couple times on flat stretches.

         Once I can wind it up after more miles, I may find I need to go to the next bigger main, but right now 45 in 4th is smooth as silk & it pulls very quickly to 55 for very short periods.

          It's a smooth running little bastard & I have none of the problems I hear here. Hear, hear!

           Good luck with yours.

PS: Did your needle have the plastic collar on it when you first took the carb apart?
I wish now I had broken it off Day One & dialed it in using the notches.

Geo


   

[DanB]

Are you on the stock air filter?

I have the stock air box on an Electra, but am using a k&n filter. I just moved the needle one notch, and sometimes I get a little popping when downshifting. But it pulls nicely and starts fine. I'm still dialing things in. With that said, I've been thinking about the 30mm performance carb from our hosts....
Good luck on your freeway run.

[Machismo]

I have the stock air box on an Electra, but am using a k&n filter. I just moved the needle one notch, and sometimes I get a little popping when downshifting. But it pulls nicely and starts fine. I'm still dialing things in. With that said, I've been thinking about the 30mm performance carb from our hosts....
Good luck on your freeway run.
I remember reading somewhere that our stock carb has a lot of potential to perform well.
While it might be true, its definitely a test of patience!

       
         After much back & forth (I probably had the carb off & on a dozen times dialing it in) I'm back to the stock 15 Pilot & the stock 110 Main with the needle lifted two shims. My needle has the permanent plastic collar on it over the notches so I can't talk notches with you. My mixture screw is about 1 1/2 turns out.

         The bike runs perfectly set up this way & now has 600 miles. It kick starts under all conditions with one or two kicks (I never use the ES) & never dies at stop signs or pops or sputters or any other bad stuff. It pulls well in the first 4 gears up to my break-in speeds. I've only even been in 5th a couple times on flat stretches.

         
PS: Did your needle have the plastic collar on it when you first took the carb apart?
I wish now I had broken it off Day One & dialed it in using the notches.

Geo   

Thanks Geo.
Mine does have a plastic ring below the notches but i can adjust the circlip position(3 notches).
For me 15 seems to be too lean with horrible popping.

As I had earlier, this weekend was spent on getting the right pilot/fuel screw/needle set up.
I put on a 17.5 pilot, put the needle on its leanest notch(first from the top) and set out to check the bike.
There seems to be good improvement throughout the range. Popping still present but at least the bike runs good. However, there isn't the crispness i am looking for. Usually I would expect the bike to surge ahead with a good twist of throttle in the 3rd gear. It gets there but in a very gradual manner.
Idling is relatively steady.

I would love to hear if you all have this same throttle response or does it mean i need to fine tune the carb?

[St1g9203]

Help needed with my carb.

I took my bike out for a 200 mile ride, and towards the end of it, all of a sudden the bike bogs down if the throttle is twisted more than 1/4th.

Even today i noticed the same behavior, it feels like the bike is out of fuel, if the i give more than 1/4th throttle.
I haven't open the air-filter yet, could it be a dirty filter or anything more serious?

I ride a 2005 Thunderbird (AVL)
Carb - BS 26
Jets - Stock
Airfilter - Stock

[tooseevee]

Thanks Geo.
Mine does have a plastic ring below the notches but i can adjust the circlip position(3 notches).

I would love to hear if you all have this same throttle response or does it mean i need to fine tune the carb?

            I guess our federal regulations have caused the makers of this carb to do some strange (& inconsistent) things because with my carb (same as yours, a BS-29) the plastic collar covers all three circlip grooves. I don't understand how you say you can still use your grooves if the plastic collar is on the needle below the grooves.

             I have not removed the plastic collar on mine (I should have Day One)
 which means I can only go rich, not lean. After I installed the K&N & a free-flow (essentially wide open) muffler I tried many combinations of pilot, main & shims. I ended up with it just about perfect (starting, idling, running, never dieing or farting or backfiring or bogging) by returning to stock pilot & main & just having the needle lifted 2 shims (0.004") richer than the plastic collar would have it sit at. Three was way too rich & one not rich enough.

         I may find it needs a tweak after I get more break-in miles on & can nail it in 4th & get into 5th & crank it. Don't know yet. It only has 600 miles now & I've been mostly in the first 4 gears avoiding full noise. My throttle response is good across the board.

              It takes time & you can't get frustrated. By the time the bike's happy you'll know this orphan carb like the back of your hand.

 
 

[St1g9203]

I was stupid not to check the airfilter after i bought the bike.

A supremely clogged filter and overfilled engine oil, caused the bike to mis-behave.
A brand new filter/spark plug ensures everything is jolly good in my world.

thanks much,
Adi

[DanB]

I put on a 17.5 pilot, put the needle on its leanest notch(first from the top) and set out to check the bike.
There seems to be good improvement throughout the range. Popping still present but at least the bike runs good. However, there isn't the crispness i am looking for. Usually I would expect the bike to surge ahead with a good twist of throttle in the 3rd gear. It gets there but in a very gradual manner.

Machismo, how did this turn out?   I've read in a UK forum that a few folks have left the 15 pilot in, 120 mainjet and removed 0.8mm off the bottom of the slide; essentially a smaller cutout. So, I was curious how your dialing in has gone and what adjustments you've made from the above.

~dan

[barenekd]

Get an Amal. Much easier to tune!
Bare